Audion tube construction



July 2, 1935. A. s. HOPPING AUDION TUBE CONSTRUCTION Filed Nov. 26, 1928r 7 .rrrrrrrrr f1 Patented July 2, 1935- AUDION TUBE CONSTRUCTION AlvinSamuel Hopping, Bloomfield, N. J., assignor, by mesne assignments, toRadio Corporation of America, a corporation of Delaware ApplicationNovember 26, 1928, Serial No. 321,830

4 Claims.

This invention-relates ingeneral to improvements in the construction ofvacuum tubes by means of which the characteristics of cheapness, ease ofassembly, reproducibility, uniform char acteristics,-lightness, andruggedness are secured.

One of the objects of this invention involves the construction of theanode or plate electrode of electron discharge devices of the type knownas audions in the form of a spiral winding of wire.

Another object of this invention involves the construction of theelements of devices of the above type of apparatus which are very simplein structure and adapted for production in large quantities, which partsare so made as to be assembled in the correct relation only.

A further object of this invention is the production of vacuum tubeelements of this nature which in assembled relation produce a unit whichis very light and yet exceedingly strong, thus eliminating a tendency tothe production of microphonic noises and displacement of the elementsunder shock.

A further object of this invention contemplates a structure which may bemade of substantially gas free materials which can, upon treatment, becompletely degasified.

A further object of this invention involves a structure including coil,grid and plate by means of which heat dissipation is increased and thedanger of back emission is eliminated.

These and other objects, as will appear from the following disclosure,are secured by means of this invention.

This invention resides substantially in the combination, construction,arrangement, and relative location of parts, all as will be set forth inconsiderable detail in the following disclosure and defined in theappended claims.

Referring to the drawing- Figure 1 is an elevational view of the deviceshowing the relative arrangement of parts;

Fig. 2 is an elevational view taken at right angles to Fig. 1;

Figure 3 is a cross sectional view taken on the line 33 of Fig. 1looking in the direction of the arrows; and

Fig. 4 is an enlarged cross sectional view of the heater element of thetube taken on the same line.

The disclosure in the drawing of this invention is that of what is knownas an indirect heate'r type of A. C. tube but it is, of course, apparentthat many of the features of construction of the device as disclosed areapplicable to all forms of electron discharge devices. It is usual inthe present construction of these devices to employ an anode or plateelectrode consisting of a sheet of metal formed into a cylinder ofcircular or other cross sectional configuration. The metal usuallyemployed for the plate electrode is nickel which is used extensivelybecause of its cheapness, this being the main consideration since nickelis not the best metal for the plate electrode when considered withrespect to its electrical characteristics. The best common metalselectrically for the plate or anode of an electron discharge device aretungsten and molybdenum. Heretofore, these metals have not been used insolid plate construction because of their high cost, difiiculty ofpreparation, and inadaptability for the operations thereof trans formingthem into plates. conservatively it may be said that a tungsten ormolybdenum plate of average size would cost in the neighborhood ofseveral dollars which, of course, is prohibitive. One of the features ofthis invention is the employment of tungsten or molybdenum in the formof a small wire shaped to form a helical coil. It is now relatively easyand cheap to produce tungsten or molybdenum in the form of fine wires.Thus a plate electrode comprising a fine coil of tungsten or molybdenumwire would only cost a few cents to construct. In addition, such a plateelectrode is strong, exceedingly light, and adapted to readily dissipatethe heat generated by the cathode or heater. It has been known before toconstruct plate electrodes in the form of a fine wire mesh but the wiresin the mesh are usually not closer than five thousandths of. an inch,while the wound helical plate may have the wires as close as onethousandth of an inch. In addition, fine mesh grids have a tendency tobuckle and do not as readily dissipate the heat generated. Otherimproved features of construction will be apparent from the followingdetailed disclosure.

Referring to the drawing in which one embodiment of this invention hasbeen given, the device is shown comprising a socket I having thedepending contact prongs 2, 3, 4, 5 and 8. These prongs are connected tothe various electrodes of the device in a manner well known in the artand need not be gone into in detail in this case. Cemented in the socketl is the evacuated vessel 1 having reentrant stem tube 8 in the press ofwhich is supported in a vertical position all of the electrodes. The twomain supports comprise two straight wires 9 and i0 securely held in thepress of the stem tube and extending vertically therethrough.

Mounted transversely on the two supporting wires 9 and I through whichthey pass are the insulating plates II and I2. These insulating plates,which in the best form of construction are .made of mica, have a numberof holes punched therein so that they may slide over the supports 9 andI 0. The lower spacer or plate ll may contact with flattened portions ofthe support to limit its downward movement. other holes in the spacers II and [2 are two short straight rods l3 and I 4 around which is woundthe wire l6 forming the plate electrode of the tube. In actualconstruction the turns will be much closer together but have been shownas they have in the drawing so as to not confuse them with the gridcoil. These turns, as is usual in the art, are welded to the supportingwires. The supporting wire l3 has a curved extension l which is weldedto the support 9 which, together with the lead in wire and correspondingprong, provides a circuit to a point external of the tube for the plate.In a similar manner the grid is mounted on two wire supports l1 and I8extending through holes in the spacers. Support I1 has a curvedextension I9 which is welded to the support I 0 which, together with thelead in wire and corresponding prong, provides a circuit external to thetube for the grid. The grid comprises a winding of wire each turn 20 ofwhich is welded to the supports. These two helical coils are made oftungsten or molybdenum in accordance with the principles of thisinvention.

The heater in this case comprises a resistance wire 2| which is mountedin a ceramic enclosing member 23. This ceramic enclosing member orsupport comprising a small solid rod of some insulating material, suchas isolantite, which has two parallel longitudinal boresextendingtherethrough through which the resistance wire 2! bent in the form of ahairpin is threaded. The terminals of this resistance wire,- which formsthe heater, extend to two of the depending prongs. The insulatingsupporting rod 23 is covered for the greater part of its externalsurface with a suitable metallic sleeve 30 which in turn is covered withany suitable electronically active material forming a coating 24 in themanner now well known in this art. As shown in Fig. 2 the coating 24 isin electrical contact with this sleeve 30 of conducting material 25which is welded to a short projecting wire 25, which is in turn weldedto a wire 22 fastened to the press. This wire 22 is likewise connectedto one of the prongs of the base. The construction of the heater andcathode surface is shown in better detail in Fig. 4. Also welded to thesupporting wire 9 is a short wire 26 which supports at its lower end asmall metallic open ended cup 21 in which the getter" is placed. Thissmall cup opens downwardly so that when the getter is flashed to removeany residual gases within the tube the interor surface of the vessel 1is not coated so as to make it In the bestpractice this small opaque tolight. container 21 will have the plane of its open end below the planeof the top edge of the socket so that the so-called silvering effectwill not occur on any substantial portion of the vessel which extendsabove the socket.

The advantages of this construction as pointed out at the beginning ofthis disclosure are now apparent. I am, of course, well aware that manychanges in the details of construction and relative arrangement of partswill readily occur to those skilled in the art ,and I do not, therefore,desire to be limited to this detailed disclosure which has been givenfor purposes of illustration but rather to the principles and scope ofthe invention as it is defined in the appended claims.

What I seek to secure by United States Letters Patent is:

1. An electron discharge device comprising a central sleeve-likecathode, a first wound wire electrode surrounding said cathode, a secondwound wire electrode surrounding said cathode, a first insulator memberfor spacing the upper ends of all said electrodes, a second insulatormember for spacing the lower ends of said electrodes, each of saidinsulators having a perforation through which the opposite ends of saidcathode pass for maintaining said cathode central with respect to saidwound electrodes.

2. An electron discharge device comprising an evacuated container havinga press portion, a

' sleeve-like metal cathode, a pair of wound wire grid-like electrodessurrounding said cathode, a pair of metallic wires serving as the solesupport for said grid-like electrodes from said press, and an insulatordisc through which said cathode passes for maintaining said cathodecentral with respect to said grid-like electrodes.

3. In a vacuum tube a pair of spaced apart insulators, a cathodeextending between said insulators, a grid having a supporting rodbetween said insulators and extending through an opening in one of them,the end of said grid rod being bent at an angle at'the opposite side ofsaid insulator, a press, a plurality of support rods sealed in saidpress andpassing through aligned openings in said insulating members,the bent end of said grid support rod being welded to one of saidsupport rods.

4. An electron discharge device comprising an enclosing glass envelope,a metallic tubular cathode having an exterior coating of alkaline earthoxides thereon, a heater element disposed in said cathode, currentconducting leads for said heating element extending through saidenvelope, a perforated anode, and a dielectric shield member disposedbetween said anode and said heating element current conducting leads.

ALVIN SAMUEL HOPPING.

